Natural forest disturbance and change in the Brazilian Amazon

Abstract

Landsat Thematic Mapper images covering the entire 3.9 million km² of forested Brazilian Amazon reveal natural change and disturbance occurring on a scale of decades to centuries. These include: 92,000 km² of bamboo forests undergoing synchronous mortality and regrowth; 1500 km² of recently active dune fields; 900 km² of recent downburst blowdowns; > 500 km of recent forest fire scars; and an unknown area of forest mortality from flooding of high ground and alluvial forests. Fire subclimax fern savannas created by Yanoama Indians cover an additional 600 km². Natural and indigenous disturbances and synchronized phenologies are therefore responsible for a dynamic spectral bahavior in large portions of the Amazon Basin. Disturbances and disturbance indicators not easily detected include blowdown sites > 30 yrs old, blowdowns < 30 hectares in size, liana forests and babassu palm forests.